This article considers what might be implied in the term ‘immersive theatre’, asking what kinds of ‘interior’ audiences are invited to become immersed in. To facilitate my argument I draw on performances by two London-based theatre companies, Shunt and Punchdrunk, as examples of immersive theatre which use architectural interiors: extensive environments which audiences explore in order to find the performance, and sometimes to give performances themselves. I begin with a description of how these physical interiors and the audience member's movement through them becomes part of the dramaturgy of the work, before moving on to a critique of the term ‘immersive’. This critique is initially based on analysis of its metaphorical character, using an approach derived from cognitive linguistics, and is developed through Josephine Machon's (syn)aesthetics and Heidegger's phenomenological aesthetics.